The present invention relates to a method of instantaneously initiating the scarfing process of to eliminate the surface defects of a steel material, and also to a consumable electrode used for said method. The scarfing equipment is generally used in steel mills and the like for removing the defects on steel products such as slabs, blooms, or billets. The kind of scarfing equipment for treating steel material of high temperature is called a "hot scarfer" which instantaneously starts the scarfing process with high-pressure oxygen jetted from the scarfing nozzle. However, for treating cold material, there must be used a so-called cold scarfer after the scarfing position has been heated up to the temperature, at which oxidation may be used to scarf the steel.
Usually in the case of scarfing cold material, the scarfing position must be heated more than 10 seconds. Such a long heating time not only lowers the operation efficiency but also makes it impossible to practice the so-called "flying start of the scarfing operation", according to which the scarfing operation is started as the scarfing machine is moving, or without stopping the movement of the material to be scarfed which factors represent disadvantages in the conventional method of scarfing cold material.
In order to shorten the heating time, the following methods are publicly known:
First, there is known a method of providing in front of the scarfing nozzle, a nozzle for jetting a metal powder such as iron into the pre-heating flames, thereby producing a great volume of heat energy by the combustion of such metal powder with oxygen as well as mechanical energy due to the jetting of such metal powder, which makes for the speedy local heating of the scarfing position. Secondly, there is known a rod of method of feeding a storting small diameter in front of the scarfing nozzle until it contacts the scarfing position, so as to melt the tip of said rod with pre-heating flames issued from the scarfing nozzle which results in the production of molten drops for heating and melting material at the scarfing position.
However, these methods are successful only in shortening the heating time more or less, but not in achieving an instantaneous initiation of the scarfing process. According to the first method, 4 to 5 seconds are required before the start of scarfing operation and according to the second method, 6 to 10 seconds are required. Such lengthy heating times do not make it possible to initiate the so-called in the scarfing operation.